Originally Posted by JazzRoc
Ah. I see where you're coming from.
Of course it's work for a human arm. A constant stream of work is being done maintaining muscular tension. That you might call STRAIN. But muscles work by electrochemical pressure, and their electrical "circuits" are very lossy. A constant stream of ATP (the body's gasoline) is required to maintain each muscular fibre's position. It gets "burnt" to lactic acid which is flushed to the kidneys.
But consider a rock on a plain on the Moon.
An old BIG rock which might have whacked down in an aftermath of an early asteroid strike and would have sat there for a million years. Straining. Consuming nothing. You need to understand the difference between plasticity and elasticity as well, by the sound of it.
Has it done a virtually infinite amount of work?
Or the Earth? The whole of it is in strain searching to fall to the centre. An almost infinite amount of work?
No. Work is done raising up a weight up using a pulley. Or the same amount of work done when it is released and falls back to where it was lifted from. Technically described as accelerating a mass over a period of time, and thus involving the dimension of length. In free fall the acceleration will be the local gravitational constant for the gravitational body. The product of the particular mass of that body, the acceleration, and the distance travelled will determine the work done.
In deep space, the acceleration will be determined by the mass divided by the force. The work done (say by a rocket engine) would then be the mass times times acceleration times distance the rocket engine works over.
Get your head round it. Pick up a schoolbook on mechanics and read and understand it.
Again I had to re-edit my work: I really must pick up a physics book again.
Why does a gravitating body ONLY do work on an object when it is moving? The gravitational field is there all the time.
Forget about nerves and ATP, consider the following example. I am on a steep hill in my car and I take the handbrake off. Instead of rolling back down the hill I have my clutch part way out and the accelerator pedal slightly depressed. The revs of the engine combined with clutch control stops the vehicle rolling back down the hill. The car engine is therefore doing work but yet the car is not moving. How is this possible?
Going back to the example of the rock sat on the surface of the Moon, on a quantum level you could indeed consider that the gravitational field was doing work on the stationary rock. Between atoms there is mainly space and what stops the atoms of the rock and the lunar surface combining in the gravitational field is an electrostatic repulsion in the other direction. This electrostatic repulsion is continuous and therefore the electric charges in the atom are continually doing work.